#lang racket

(define (caculate-delta a b c)
  (sqrt (- (* b b) (* 4 a c)))
  )

(define (quadratic-roots a b c)
  (cond
    [(= a 0) 'degenerate]
    [(< (* b b) (* 4 a c)) 'none]
    [(= (* b b) (* 4 a c)) (/ (- 0 b) (* 2 a))]
    [else (cons (/ (+ (- 0 b) (caculate-delta a b c)) (* 2 a))
                 (cons (/ (- (- 0 b) (caculate-delta a b c)) (* 2 a)) empty))
            ])
  )

; Test
(quadratic-roots 1 -3 2)